This invention relates generally to an apparatus and process for depositing thin films of coating material onto a substrate and more particularly for selectively applying controlled amounts of coating material in registration with portions of corrugated sheet material, substantially flat sheet material, or formed sheet material.
Thin films have an enormously, varying range of industrial applications. For example, thin films of gold, silver and chromium are used for decorative purposes, thin films of aluminum and nickel-boron have been used for corrosion protection, and thin films of magnesium fluoride, aluminum oxide and silicon oxide have all been used as non-reflective coatings for optical lenses.
Kirk-Othmer's "Encyclopedia of Chemical Technology", 3rd edition (1980) Vol. 10, pages 247 to 283 describes the following types of process for depositing thin films:
A. Deposition of Films from Solution
1. Electrolytic deposition-cathodic and anodic films.
2. Chromate conversion coatings.
3. Electroless plating.
4. Polymeric coatings.
B. Vacuum Deposition of Films
1. Evaporation of inorganic materials.
2. Evaporative coating with polymers.
3. Vapour-phase polymerization.
4. Sputtering.
5. R-f sputtering of polymers.
6. Ultra-violet irradiation, photopolymerization.
C. Deposition of Films in Gaseous Discharge
D. Deposition of Films at Atmospheric Pressure
1. Metallo-organic deposition.
2. Electron-beam polymerization.
3. Gamma irradiation.
4. UV solid polymerization.
The present invention provides a method of depositing films which falls into none of the above-mentioned categories. The method and apparatus has application to a vast range of corrugated sheet material, substantially flat sheet material, or formed sheet material and coating materials.
Precious and semi-precious metals such as chromium, palladium, platinum, silver, and gold are often applied to corrugated surfaces, e.g., catalytic converters. It is desirable to apply these metals at the precise location in the minimum amount necessary so as to increase the efficiency of the coated apparatus and permit the welding, brazing, or bonding of the non-coated areas, while minimizing the amount of precious metals utilized.
Conventional methods apply coatings to individual sheets of substantially flat material, or on coils of substantially flat sheet material, in a continuous film or non-registration patterns. One shortcoming of these prior art systems is that they are labor intensive. Another shortcoming is that they are slow. Yet another shortcoming is that it is difficult to control the amount and location of material applied which may result in uneven application and waste.